When one partakes in the act of inhaling cocaine through the nostril. The "hoover" section of the saying comes from the vacuum brand, while schneef is a variation on the word sniff or to sniff. "Schneef" is slang for cocaine.
Schkeet is everything. Noun, adjective, verb, adverb, pronoun. It means whatever you make of it. Enunciation can also affect the meaning. Use with caution, as it is a dirty word to some.